Strabismus is a common condition in which the eyes do not align properly, turning inward, outward, upward or downward. Two to four percent of children have some form of it. Some cases can be treated with glasses or eye patching; other cases require eye muscle surgery. But the treatments don’t address the root causes of strabismus, which experts believe is neurologic.
For decades, Elizabeth Engle, MD, in Boston Children’s Hospital’s F.M. Kirby Neurobiology Center, has been studying rare forms of strabismus, such as Duane syndrome, in which strabismus is caused by limited eye movements. Her lab has identified a variety of genes that, when mutated, disrupt the development of cranial nerves that innervate the eye muscles. These genetic findings have led to many insights about motor neurons and how they develop and grow.
More recently, with postdoctoral research fellow Sherin Shabaan, MD, PhD, Engle’s lab has been gathering families with common, non-paralytic strabismus, in which both eyes have a full, normal range of motion yet do not line up properly.
Such “garden variety” forms of strabismus have been much harder to pin down genetically. …
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Elizabeth Engle used to wait in peoples’ driveways until midnight, hoping to enroll them in her genetic studies of eye-movement disorders. She landed there by chance: during her neurology residency, she saw a little boy whose eyes were frozen in a downward gaze. Wanting to find a solution to a disorder that others had written off, she talked her way into the muscular dystrophy genetics lab of Alan Beggs and Lou Kunkel at Children’s.
Why muscular dystrophy? That tragic muscle-weakening disease somehow spares the eye muscles. Engle thought if Beggs and Kunkel took her on, she could answer two questions at once – what was protecting the eye muscles in muscular dystrophy, and what had caused the little boy’s fixed gaze and droopy eyelids. Plus, she needed laboratory training to study the samples she’d started gathering. “I didn’t have a PhD and was never officially trained in the lab,” she once said. “I didn’t even know how to make chemical solutions.” …
Children with “lazy eye,” or amblyopia, have structurally intact eyes that may appear normal. But one eye isn’t used, generally because of a subtle misalignment. Unless someone notices this early enough, the “lazy” eye can slowly go blind, simply because the brain hasn’t received proper stimulation from it. It’s learned to ignore input from that eye.
“While amblyopia is easy to treat if you get to the kids early, it’s hard for us as ophthalmologists to get to the kids early because often the condition isn’t detected in the pediatric office,” says David Hunter, chief of ophthalmology at Children’s Hospital Boston.
Treatment consists of patching the sound eye, forcing the child to use the weaker eye. Ideally, this should be started before age 5, when the brain is still able to relearn; once a child reaches 8 to 10 years it’s often too late to restore his vision. …